Length Converter
Convert length and distance across fifteen units, from millimetres and inches to kilometres, miles and nautical miles; type in one box and every other updates. One inch is exactly 2.54 cm by definition, so 5 ft 11 in is precisely 1.8034 metres. A nautical mile is 1,852 metres and a land mile 1,609.344.
Updated
How to use the Length Converter
- 1Type a value into any box — every other unit updates as you type.
- 2Use the swap button to flip the two headline units.
- 3Copy any result with the button beside it.
- 4Adjust the decimal places if you need more or less precision.
How it works
All length units are defined against the metre, which since 1983 has been defined by the speed of light. The imperial units are not independent measurements: since the 1959 international yard and pound agreement, the inch is defined as exactly 25.4 millimetres, which makes every other imperial length exact too.
That exactness is why 5 feet 11 inches converts to precisely 1.8034 metres rather than something that drifts in the last digit. The nautical mile is the one unit defined differently — exactly 1,852 metres, chosen to approximate one minute of latitude.
Conversion works by taking your value to a single base unit and then out again, so every pair of units is consistent with every other. Values are calculated at full double precision and only rounded for display, which means round-tripping a number through two conversions returns what you started with.
The formula
- factor
- how many metres one of that unit represents
- metre
- the base unit every factor is defined against
1 inch = 0.0254 m exactly; 1 mile = 1609.344 m exactly; 1 nautical mile = 1852 m exactly.
Worked example
Converting a height of 5 ft 11 in to metres
- 5 ft 11 in = 71 inches
- 71 × 0.0254 = 1.8034
Result: 1.8034 metres, or 180.34 centimetres.
Common length conversions
Calculated with the exact definitions the converter uses: 1 inch is 2.54 cm and 1 mile is 1.609344 km.
| From | Equals |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 30.48 cm |
| 1 foot | 0.3048 m |
| 1 yard | 0.9144 m |
| 1 mile | 1.6093 km |
| 1 cm | 0.3937 inches |
| 1 metre | 3.2808 feet |
| 1 metre | 39.3701 inches |
| 1 km | 0.6214 miles |
| 100 metres | 109.3613 yards |
| 5 km | 3.1069 miles |
| 10 km | 6.2137 miles |
| 5 ft 6 in | 167.6 cm |
| 5 ft 10 in | 177.8 cm |
| 6 ft 0 in | 182.9 cm |
Tips and common mistakes
- For heights in feet and inches, convert everything to inches first: 5 ft 9 in is 69 inches.
- Use the nautical mile only for sea and air navigation; it is not the same as a land mile.
- Raise the decimal places for engineering work and lower them for everyday measurements.
- The inch is exactly 2.54 cm, so conversions between metric and imperial are exact, not approximate.
Frequently asked questions
How many centimetres are in an inch?
How do I convert feet and inches to centimetres?
Why is a nautical mile different from a land mile?
How accurate are these conversions?
How many feet are in a metre?
How many kilometres are in a mile?
How tall is 170 cm in feet and inches?
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